The primary objective of these studies is to elucidate the mechanism(s) for the oxidation reactions catalyzed by the cytochrome P-450 dependent mixed function oxidases. Since chloroperoxidase isolated from Caldariomyces fumago exhibits striking structural and functional similarities to cytochrome P-450, it will be used as a model system to study the mechanisms of oxygen activation and substrate oxidation by the microsomal enzyme system. The initial phases of experimentation will be concerned with studies on the various types of oxygen utilized, substrate specificity, and indentity of products. The binding of substrates and other ligands to chloroperoxidase will be investigated by optical, ESR, and NMR spectroscopy in order to learn more about the substrate binding sites, the interaction of substrates with the heme-iron and the porphyrin ring, and the interaction of various substrates with enzyme-bound oxygen.